1. Field of the Invention
The present invention relates to an overhead-traveling carrying apparatus which travels along a track which is installed overhead, and which conveys objects to be carried in a suspended state between semiconductor manufacturing apparatuses which are disposed in a clean room.
2. Background Art
In production facilities which conduct the manufacturing of semiconductor devices, carrying devices are employed which automatically conduct the conveyance of semiconductor wafers among a variety of apparatuses; track-type carrying apparatuses are often employed as such carrying apparatuses. In general, in track-type carrying apparatuses, the structure is such that carriages travel along tracks which are installed either overhead or on the floor surface, and normally the semiconductor wafer processes are conducted to the side of the tracks.
Generally, semiconductor devices are produced via processing involving several hundred processes in which a semiconductor wafer comprising silicon or the like is conveyed back and forth between a variety of semiconductor manufacturing apparatuses (wafer processing apparatuses, storage apparatuses, work platforms, buffer apparatuses, and the like) by an overhead-traveling carrying apparatus or the like.
This will be explained below with reference to FIG. 6. For example, in an overhead-traveling carrying apparatus for semiconductor manufacturing apparatuses in a clean room, carriages 3 with attached hoists, which travel along an overhead track 1 which is not depicted, are employed, and processing is conducted by carrying wafer carriers 6 with semiconductor wafers 2 loaded thereon between the semiconductor manufacturing apparatuses 7, or between the semiconductor manufacturing apparatuses 7 and the stocker 7A.
The carriages 3 with attached hoists depicted in the figure comprise a traveling part 3a, which travels along track 1, and a hand 5, which is suspended in such a manner as to be fully raised or lowered by a hand suspending part 4 which is provided on this traveling part 3a; the wafer carrier 6, which is placed at the load port 8 of the semiconductor manufacturing apparatus 7, is grasped by hand 5, and after the hand suspending part 4 lifts the hand 5, this is carried along the track 1 by traveling part 3a. 
Within this clean room, as shown in the figure, a plurality of semiconductor manufacturing apparatuses 7 are arranged in a parallel fashion along the track 1 which is provided overhead, and the wafer carriers 6 are grasped on load port 8 of each semiconductor manufacturing apparatus 7 by the plurality of carriages 3 with attached hoists, and are carried to other semiconductor manufacturing apparatuses 7.
The carrying of the semiconductor wafers 2 by the overhead-traveling carrying apparatus described above is conducted in the following manner. First, the carriage 3 with an attached hoist travels along track 1, and stops above a load port 8 which has a wafer carrier 6 which is to be carried. Next, the hand suspending part 4 is lowered and the hand 5 descends, and the wafer carrier 6 is held by the hand 5. Then, the hand suspending part 4 is hoisted and the wafer carrier 6 is removed from load port 8, and after this has been hoisted to a maximum height, the carriage 3 with an attached hoist again begins to travel.
Next, the carriage is again stopped above the load port 8 of a stocker 7A or another semiconductor manufacturing apparatus 7 which is to conduct the subsequent process. The hand suspending part 4 is then lowered and the hand 5 descends, and after the wafer carrier 6 has come completely to rest on the load port 8, the hand 5 releases the wafer carrier 6 and the hand suspending part 4 is again hoisted, lifting hand 5, and a transition is effected to the next carrying operation.
In such overhead-traveling carrying apparatuses, in order to avoid problems such as the dropping of objects to be carried or contact between objects to be carried and obstacles (not depicted in the figure) such as humans or objects which were not placed carefully, during the lowering of the objects to be carried, a variety of countermeasures thereto have been considered from the point of view of the raising and lowering relationship between the objects to be carried by wafer carriers 6 and the load ports 8.
A conventional proposal for such countermeasures will be discussed below with reference to FIGS. 7 through 10. This countermeasure proposal was announced as a joint guidance of J300 (Japan 300 mm Semiconductor Technology Conference) and I300I (International 300 mm Initiative). Those structural parts which are identical to those explained by FIG. 6 are given identical reference numbers, and an explanation thereof will be omitted.
FIG. 7 shows a case in which an emergency stoppage switch 9 is provided in the vicinity of a semiconductor manufacturing apparatus 7 (in the figure, this is provided on the upper surface of load port 8), and prior to the occurrence of a problem, or after a problem has occurred, an operator not depicted in the figure presses this switch, and thereby stops the raising or lowering operation of the hand 5 or the wafer carrier 6. For the purposes of the explanation, these proposals will hereinafter be referred to as countermeasure proposal A.
FIG. 8 shows a case in which a light curtain 10 is placed in front of load port 8 using optical sensors, and when this light curtain 10 is disrupted by an obstacle such as a person or the like, the semiconductor manufacturing apparatus 7 detects the abnormality and stops the raising or lowering operation of the wafer carrier 6. For the purposes of explanation, this proposal will hereinafter be referred to as countermeasure proposal B.
FIG. 9 shows the case in which walls 11 and manual doors 12 are provided above load port 8, and the space above load port 8 is thus covered. When it is necessary to gain access to the area within load port 8 for the purposes of maintenance or the like, the manual doors 12 may be opened manually; a sensor 13 which detects this open state is provided in manual doors 12, and in the state in which manual doors 12 are opened, the sensor 13 detects this and halts the raising or lowering operation of the wafer carrier 6. For the purposes of explanation, this proposal will be referred to as countermeasure proposal C.
FIG. 10 shows the case in which, in place of the manual doors in countermeasure proposal C, automatic doors 14 which open and close automatically are provided. In this proposal, as well, sensors 13 are provided in the same manner as in countermeasure proposal C. For the purposes of explanation, this proposal will be referred to hereinbelow as countermeasure proposal D.
However, these conventional countermeasure proposals A, B, C, and D have the following problems, and have not reached practical application.
In other words, countermeasure proposal A requires the observation of all of a large number semiconductor manufacturing apparatuses 7 by operators, and requires instantaneous decisions by those operators, so that it is not appropriate for continuous employment.
Furthermore, countermeasure proposals B, C, and D all require the constructing of countermeasures at more than 1,000 spots in order to be applied to all of the load ports 8 (generally, there are 2 to 4 of these for each apparatus) of a large number of semiconductor manufacturing apparatuses 7 (normally, between 300 and 400; furthermore, there are several tens of the carriages 3 with attached hoists in this case), so that this causes problems in that the manufacturing costs or maintenance costs of the semiconductor manufacturing apparatuses 7 increase.